It has heretofore become well known to provide a system for encoding data prior to transmission and then decoding the same after transmission to recover the data and hence facilitate the orderly transmission of intelligible information. It has likewise heretofore become well known to store encoded information either before, after, or as a part of, transmission and then recover the same as needed or desired.
Included among such systems are systems that utilize pulse width modulation as well as systems that modulate the spacing between the pulses for data encoding purposes. The encoded data are then demodulated after transmission and heretofore such demodulation has commonly been carried out by use of a conventional unit such as, for example, a conventional pulse-width demodulator or demultiplexer.
However, it has been found that the transmission channel can impose a time distortion that can make it difficult or, in some instances, impossible to recover the data from an encoded data train. If the data are recorded on magnetic tape, for example, speed variations in the tape will alter the time relation between the pulses, or parts of a pulse or pulses, that contain the encoded data. In like manner, in wireless transmission, variations in path length for the radio frequency waves between the point of transmission and reception can alter the temporal relations between the pulses that contain the encoded data.